The present invention relates generally to cleaning devices and, more particularly, to wet abrasive blasting systems used for cleaning, preparing surfaces, removing coatings, and other abrasive blasting applications.
To remove corrosion or coatings from a substrate such as steel or concrete in order to restore, paint, or clean the substrate, cleaning systems are used. In certain applications, abrasive blasting systems should be able to clean or remove corrosion or coatings without damaging the underlying metal or other substrate. In other applications, a certain degree of surface roughness (called profile) may be desired to assure new paint or coating adhesion.
The use of dry, hard abrasives, such as those used in conventional sand blasting, may result in excessive surface roughness to the point of causing damage to the substrate. Typical blast materials are hard (6 to 9 on Mohs Scale of Mineral Hardness) and abrasive in order to increase the efficiency of the blasting operation. Soft blast materials (generally less than 6 on the Mohs scale), such as agricultural products which can include crushed walnut shells, rice hulls, corn cob, and pistachio shells, plastic or glass particles are sometimes used to reduce substrate surface damage. (See also U.S. Pat. No. 6,609,955 (Farrow), regarding a method for removing surface coatings).
FIG. 1 depicts a conventional current wet-abrasive system 1 that is used to reduce the amount of airborne dust and minimize surface damage, even while using hard abrasives. Wet-abrasive systems rely on a method to force a mixture of water and the abrasive media into the compressed air-stream in a controlled manner. In particular, a blast pot or pressure vessel 2 is manually charged with a liquid, typically water through a water inlet 4. The solid abrasive (not shown) is manually entered into the blast pot 2 via an opening 5 in the top the blast pot 2 and wherein this opening 5 is then manually sealed, using a standard bung assembly 16; as shown in FIG. 1, this bung assembly 16 is pulled up and manually held in place until enough pressure is built up in the blast pot 2, thus forming the water-media mixture 3 (also referred to as the “slurry”) within the blast pot 2. The blast pot 2 is then manually purged of air via a first manual valve 6 (a second manual valve 6A is also provided for depressurizing the blast pot 2 when required). The blast pot 2 is fully pressurized with water provided via a pneumatic water pump 18 connected to the water inlet 4. The flow of pressurized water forces the slurry 3 out of the blast pot's slurry outlet 7 at a controlled rate and through piping 8 that is connected to the outlet 7; the piping 8 comprises a manual slurry valve 9 followed by a water injection port 10 (for use during a washdown process) which is then followed by a diaphragm valve 11. The piping 8 is connected a T-shaped manifold 12 having a first end 13 that is connected to a compressed air source 17 which is followed by a blast regulator 14. Thus, the flow of pressurized slurry 3 combines with the compressed air to form a three phase blasting stream of abrasive, water and air and directed through a blast output 15 into a blast hose (not shown) coupled to the blast output 15 and this blasting stream is directed with the blast nozzle (also not shown) to the surface (not shown) to be cleaned.
However, these manual procedures, if done incorrectly, can create inconsistent flow or air pressure in the mix and cause erratic behavior of the wet abrasive blasting system and an inefficient blasting process. Thus, there remains a need for a system and method for eliminating these manual procedures to provide a consistent and efficient wet abrasive blasting stream.
All references cited herein are incorporated herein by reference in their entireties.